Preliminary treatment of metal plates for the production of printing plates



Patented Dec. 16, 1930 UNITED STATES PATENT OFFICE FRIEDRICH ULIJMANN, OF ZWICKAU, GERMANY PRELIMINARY TREATMENT OF METAL PLATES FOR THE PRODUCTION O1? PRINTING PLATES I No Drawing. Application filed March 7, 1927, Serial lie-173,615, and in Germany March 10, 1826.

It is a generally known fact that metal plates as carriers for light-sensitive preparations for the manufacturing of photo-mechanically obtained printing 'blocks react unfavorably upon the preparations applied on the same. This circumstance has proved to be. very inconvenient inexperiments for making phototypes on zinc plates, and it has been proposed to reduce the action of the metal on chromate preparations by a suitable preliminary treatment of the metal.

I have succeeded in reducing the unfavorable influence of the metal by treating the metal plates with diluted chromic acid, by pouring on celluloid layers, by bathing the metal plates in alum and diluted nitric acid, but it has not been possible hitherto to suppress this unfavorable influence completely so that it seemed advisable, to thoroughly examine the behavior of the metal with regard to chromate preparations, in order to discover a new method of making the metal as carrier for light-sensitive coatings by a suitable treatment as indifferent as possible with regard to these coatings.

The present invention is the result of. these experiments. It has been found that salt solutions of metals, which incline to easily form double salts and which act upon metallic zinc are specially suited for the reliminary treatment.

The method of preparing zinc plates has proved to be suitable for metallographic purposes. In comparison with the working method hereto used this preliminary preparing for metallographic purposes shortens the workmg time and presents further the advantage of increasing by the preliminary preparation of the durability of the metallographic plate.

An example of carrying out the improved method is as follows v The zinc plate, which has'been well cleaned and rendered free of fat, is placed for a short time, about to 2-4 minutes, into a bath of a solution of, for instance, 40% aluminium chloride, and subsequently well washed and dried. After this treatment the plate is ready to receive the chromate coating.

in treating the zinc plates with an aluminium chloride solution.

In testimony whereof I aflix my signature FRIEDRICH 'ULLMANN 

